If you are having issues with authorizing our plugins, you can try using another DAW to see if the plugin authorizes there.
If you don't have another DAW, you could use GarageBand, which comes with the current and recent versions of Mac OSX. Or you could try Reaper if you are on Windows or Mac, which has an unlimited free trial period.
GarageBand does make it kind of difficult to find third-party plugins. Here's an article that explains how to do it.